One thing to remember first is....This is a process you handle without snakes in the rack!!! I would tape your probe directly on the heat tape. The best way to get temps you want is to set your stat to say 90 degrees and meter temps in side the tub on the hot side(give the tub and rack time to heat up before you start metering and adjusting). Most likely your tub won't read 90 inside, it will probably be a bit cooler once the temps stablize. So if you set your stat to 90 and the tub is reading 88, then of course if you want your hot side to read 90, you will take your stat up to 92 to make up for the difference. I hope this helps you. Again, don't put you animals in the rack till you are done with metering and adjusting your rack!